1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and a system for configuring an Internet Protocol (IP) address in a wireless communication system.
2. Description of the Related Art
In the 4th Generation (4G) communication system, which is the next communication system, active research is being carried out in order to provide users with various Quality of Services (QoSs) having a transmission speed of about 100 Mbps. A representative of the 4G communication systems is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.
Meanwhile, a mobile Internet service, that is, the Wireless Broadband (WiBro) communication system, has a standard which is compatible with the IEEE 802.16 communication system standard. The WiBro communication system provides a high speed data service through various types of Portable Subscriber Stations (PSSs) in an indoor or outdoor stationary environment or in a mobile environment of walking speed or middle/low speed (about 60 km/h). The WiBro communication system is currently implemented in connection with the Internet Protocol version 6 (IPv6), which is the next generation address system.
Hereinafter, a network structure of a typical WiBro communication system will be described with reference to FIG. 1.
FIG. 1 illustrates a network structure of a typical WiBro communication system.
Referring to FIG. 1, the WiBro communication system includes a PSS 100 corresponding to mobile stations of the IEEE 82.16 communication system, a plurality of Radio Access Stations (RASs) 110, 120, 130, and 140 corresponding to base stations of the IEEE 82.16 communication system, Access Control Routers (ACRs) 150 and 160 corresponding to base station controllers of the IEEE 82.16 communication system, an Authentication Authorization Accounting (AAA) server 170, and a Home Agent (HA) 180.
The RAS is an element which is located at a terminal of a wire network and performs transmission/reception with the PSS through a wireless interface. The RAS supports the mobility of the PSS and manages and controls wireless resources. The ACR manages Medium Access Control (MAC) addresses, connection identifier and IP addresses of the PSSs in a lower network stage, controls the PSSs and RASs, performs IP packet routing and authentication/security tasks, and provides QoS to the PSS. The AAA 170 performs authentication, authorization, and accounting for the PSS. The HA 180 stores address information of the PSS.
When the PSS 100 moves to a new RAS of ACR #2 160 which has an IP subnet different from that of RAS #1 110 of ACR #1 150 to which the PSS 100 currently belongs, the PSS 100 must perform a network reentry process. Hereinafter, the network reentry process will be described with reference to FIG. 2.
FIG. 2 is a signal flowchart illustrating a network reentry process between a PSS and an RAS in a typical IEEE 802.16/WiBro communication system.
Referring to FIG. 2, according to movement of the PSS 200 to a new RAS 250, the PSS 200 receives a preamble of a downlink frame transmitted from the RAS 250 and acquires a system synchronization with the RAS 250. Thereafter, the PSS 200 receives base station information broadcast by the RAS 250, that is, base station information included in a Downlink Channel Descriptor (DCD) message, an Uplink Channel Descriptor (UCD) message, a Downlink MAP (DL-MAP) message, and an Uplink MAP (UL-MAP) message, thereby acquiring a downlink synchronization.
Then, the PSS 200 transmits a ranging request (RNG_REQ) message to the RAS 250 at step 202, and receives a ranging response (RNG_RSP) message, which is a response to the RNG_REQ, from the RAS 250, thereby acquiring an uplink synchronization with the RAS 250 at step 204.
After completing the ranging process, the PSS 200 transmits a subscriber station basic capability request (SBC_REQ) message to the RAS 250 as step 206, and receives a subscriber station basic capability response (SBC_RSP) message from the RAS 250 at step 208, thereby completing a basic capability negotiation process.
After completing the basic capability negotiation process, the PSS 200 transmits a Privacy Key Management (PKM) request (PKM_REQ) message to the RAS 250 at step 210, and receives a PKM response (PKM_RSP) message from the RAS 250 at step 212, thereby completing an authentication process.
After completing the authentication process, the PSS 200 transmits a registration request (REG_REQ) message to the RAS 250 at step 214, and receives a registration response (REG_RSP) message from the RAS 250 at step 216, thereby completing the registration in the RAS 250. Steps 202 to 216 correspond to the network reentry process performed in layer 2, in which it takes a long time to complete the ranging, basic capability negotiation, authentication, and registration.
After completing the process up to step 216, the PSS 200 must perform an IP address auto-configuration process for IP connection at step 218. According to the IP address auto-configuration, an IP address of a total of 128 bits is configured through a combination of a 64 bit prefix of an AR, which is included in a Routing Advertisement (RA) message periodically received by the PSS 200 from the RAS 250, and an interface identifier (ID) of a mobile node with 64 bits, that is, a 64 bit MAC address. After completing the IP address auto-configuration, the PSS 200 performs Duplicate Address Detection (DAD) in order to determine if the 128 bit IP address is being used by another PSS in the same subnet. As a result of the DAD process, when the auto-configured IP address is not yet occupied, the PSS 200 performs signal transmission/reception by using the auto-configured IP address.
As described above, when the PSS changes the subnet through movement, the PSS must sequentially perform a layer 2 network reentry process, an IP address auto-configuration process, and a DAD process. Therefore, the PSS cannot avoid interruption of communication until the network reentry process and the DAD process are completed. This problem undermines the object of the IEEE 802.16/WiBro communication system, which is to provide a seamless communication service.
Accordingly, a need exists for a system and method for reducing interruption of communication during a network entry process.